/*
 * Copyright (C) 2020 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License
 */

package com.android.systemui.util.animation

import android.animation.ValueAnimator
import android.graphics.PointF
import android.util.MathUtils
import com.android.app.animation.Interpolators

/**
 * The fraction after which we start fading in when going from a gone widget to a visible one
 */
private const val GONE_FADE_FRACTION = 0.8f

/**
 * The amont we're scaling appearing views
 */
private const val GONE_SCALE_AMOUNT = 0.8f

/**
 * A controller for a [TransitionLayout] which handles state transitions and keeps the transition
 * layout up to date with the desired state.
 */
open class TransitionLayoutController {

    /**
     * The layout that this controller controls
     */
    private var transitionLayout: TransitionLayout? = null
    private var currentState = TransitionViewState()
    private var animationStartState: TransitionViewState? = null
    private var state = TransitionViewState()
    private var animator: ValueAnimator = ValueAnimator.ofFloat(0.0f, 1.0f)
    private var currentHeight: Int = 0
    private var currentWidth: Int = 0
    var sizeChangedListener: ((Int, Int) -> Unit)? = null

    init {
        animator.apply {
            addUpdateListener {
                updateStateFromAnimation()
            }
            interpolator = Interpolators.FAST_OUT_SLOW_IN
        }
    }

    private fun updateStateFromAnimation() {
        if (animationStartState == null || !animator.isRunning) {
            return
        }
        currentState = getInterpolatedState(
                startState = animationStartState!!,
                endState = state,
                progress = animator.animatedFraction,
                reusedState = currentState)
        applyStateToLayout(currentState)
    }

    private fun applyStateToLayout(state: TransitionViewState) {
        transitionLayout?.setState(state)
        if (currentHeight != state.height || currentWidth != state.width) {
            currentHeight = state.height
            currentWidth = state.width
            sizeChangedListener?.invoke(currentWidth, currentHeight)
        }
    }

    /**
     * Obtain a state that is gone, based on parameters given.
     *
     * @param viewState the viewState to make gone
     * @param disappearParameters parameters that determine how the view should disappear
     * @param goneProgress how much is the view gone? 0 for not gone at all and 1 for fully
     *                     disappeared
     * @param reusedState optional parameter for state to be reused to avoid allocations
     */
    fun getGoneState(
        viewState: TransitionViewState,
        disappearParameters: DisappearParameters,
        goneProgress: Float,
        reusedState: TransitionViewState? = null
    ): TransitionViewState {
        var remappedProgress = MathUtils.map(
                disappearParameters.disappearStart,
                disappearParameters.disappearEnd,
                0.0f, 1.0f,
                goneProgress)
        remappedProgress = MathUtils.constrain(remappedProgress, 0.0f, 1.0f)
        val result = viewState.copy(reusedState).apply {
            width = MathUtils.lerp(
                    viewState.width.toFloat(),
                    viewState.width * disappearParameters.disappearSize.x,
                    remappedProgress).toInt()
            height = MathUtils.lerp(
                    viewState.height.toFloat(),
                    viewState.height * disappearParameters.disappearSize.y,
                    remappedProgress).toInt()
            translation.x = (viewState.width - width) * disappearParameters.gonePivot.x
            translation.y = (viewState.height - height) * disappearParameters.gonePivot.y
            contentTranslation.x = (disappearParameters.contentTranslationFraction.x - 1.0f) *
                    translation.x
            contentTranslation.y = (disappearParameters.contentTranslationFraction.y - 1.0f) *
                    translation.y
            val alphaProgress = MathUtils.map(
                    disappearParameters.fadeStartPosition, 1.0f, 1.0f, 0.0f, remappedProgress)
            alpha = MathUtils.constrain(alphaProgress, 0.0f, 1.0f)
        }
        return result
    }

    /**
     * Get an interpolated state between two viewstates. This interpolates all positions for all
     * widgets as well as it's bounds based on the given input.
     */
    fun getInterpolatedState(
        startState: TransitionViewState,
        endState: TransitionViewState,
        progress: Float,
        reusedState: TransitionViewState? = null
    ): TransitionViewState {
        val resultState = reusedState ?: TransitionViewState()
        val view = transitionLayout ?: return resultState
        val childCount = view.childCount
        for (i in 0 until childCount) {
            val id = view.getChildAt(i).id
            val resultWidgetState = resultState.widgetStates[id] ?: WidgetState()
            val widgetStart = startState.widgetStates[id] ?: continue
            val widgetEnd = endState.widgetStates[id] ?: continue
            var alphaProgress = progress
            var widthProgress = progress
            val resultMeasureWidth: Int
            val resultMeasureHeight: Int
            val newScale: Float
            val resultX: Float
            val resultY: Float
            if (widgetStart.gone != widgetEnd.gone) {
                // A view is appearing or disappearing. Let's not just interpolate between them as
                // this looks quite ugly
                val nowGone: Boolean
                if (widgetStart.gone) {

                    // Only fade it in at the very end
                    alphaProgress = MathUtils.map(GONE_FADE_FRACTION, 1.0f, 0.0f, 1.0f, progress)
                    nowGone = progress < GONE_FADE_FRACTION

                    // Scale it just a little, not all the way
                    val endScale = widgetEnd.scale
                    newScale = MathUtils.lerp(GONE_SCALE_AMOUNT * endScale, endScale, progress)

                    // don't clip
                    widthProgress = 1.0f

                    // Let's directly measure it with the end state
                    resultMeasureWidth = widgetEnd.measureWidth
                    resultMeasureHeight = widgetEnd.measureHeight

                    // Let's make sure we're centering the view in the gone view instead of having
                    // the left at 0
                    resultX = MathUtils.lerp(widgetStart.x - resultMeasureWidth / 2.0f,
                            widgetEnd.x,
                            progress)
                    resultY = MathUtils.lerp(widgetStart.y - resultMeasureHeight / 2.0f,
                            widgetEnd.y,
                            progress)
                } else {

                    // Fadeout in the very beginning
                    alphaProgress = MathUtils.map(0.0f, 1.0f - GONE_FADE_FRACTION, 0.0f, 1.0f,
                            progress)
                    nowGone = progress > 1.0f - GONE_FADE_FRACTION

                    // Scale it just a little, not all the way
                    val startScale = widgetStart.scale
                    newScale = MathUtils.lerp(startScale, startScale * GONE_SCALE_AMOUNT, progress)

                    // Don't clip
                    widthProgress = 0.0f

                    // Let's directly measure it with the start state
                    resultMeasureWidth = widgetStart.measureWidth
                    resultMeasureHeight = widgetStart.measureHeight

                    // Let's make sure we're centering the view in the gone view instead of having
                    // the left at 0
                    resultX = MathUtils.lerp(widgetStart.x,
                            widgetEnd.x - resultMeasureWidth / 2.0f,
                            progress)
                    resultY = MathUtils.lerp(widgetStart.y,
                            widgetEnd.y - resultMeasureHeight / 2.0f,
                            progress)
                }
                resultWidgetState.gone = nowGone
            } else {
                resultWidgetState.gone = widgetStart.gone
                // Let's directly measure it with the end state
                resultMeasureWidth = widgetEnd.measureWidth
                resultMeasureHeight = widgetEnd.measureHeight
                newScale = MathUtils.lerp(widgetStart.scale, widgetEnd.scale, progress)
                resultX = MathUtils.lerp(widgetStart.x, widgetEnd.x, progress)
                resultY = MathUtils.lerp(widgetStart.y, widgetEnd.y, progress)
            }
            resultWidgetState.apply {
                x = resultX
                y = resultY
                alpha = MathUtils.lerp(widgetStart.alpha, widgetEnd.alpha, alphaProgress)
                width = MathUtils.lerp(widgetStart.width.toFloat(), widgetEnd.width.toFloat(),
                        widthProgress).toInt()
                height = MathUtils.lerp(widgetStart.height.toFloat(), widgetEnd.height.toFloat(),
                        widthProgress).toInt()
                scale = newScale

                // Let's directly measure it with the end state
                measureWidth = resultMeasureWidth
                measureHeight = resultMeasureHeight
            }
            resultState.widgetStates[id] = resultWidgetState
        }
        resultState.apply {
            width = MathUtils.lerp(startState.width.toFloat(), endState.width.toFloat(),
                    progress).toInt()
            height = MathUtils.lerp(startState.height.toFloat(), endState.height.toFloat(),
                    progress).toInt()
            // If we're at the start, let's measure with the starting dimensions, otherwise always
            // with the end state
            if (progress == 0.0f) {
                measureWidth = startState.measureWidth
                measureHeight = startState.measureHeight
            } else {
                measureWidth = endState.measureWidth
                measureHeight = endState.measureHeight
            }
            translation.x = MathUtils.lerp(startState.translation.x, endState.translation.x,
                    progress)
            translation.y = MathUtils.lerp(startState.translation.y, endState.translation.y,
                    progress)
            alpha = MathUtils.lerp(startState.alpha, endState.alpha, progress)
            contentTranslation.x = MathUtils.lerp(
                    startState.contentTranslation.x,
                    endState.contentTranslation.x,
                    progress)
            contentTranslation.y = MathUtils.lerp(
                    startState.contentTranslation.y,
                    endState.contentTranslation.y,
                    progress)
        }
        return resultState
    }

    fun attach(transitionLayout: TransitionLayout) {
        this.transitionLayout = transitionLayout
    }

    /**
     * Set a new state to be applied to the dynamic view.
     *
     * @param state the state to be applied
     * @param animate should this change be animated. If [false] the we will either apply the
     * state immediately if no animation is running, and if one is running, we will update the end
     * value to match the new state.
     * @param applyImmediately should this change be applied immediately, canceling all running
     * animations
     */
    fun setState(
        state: TransitionViewState,
        applyImmediately: Boolean,
        animate: Boolean,
        duration: Long = 0,
        delay: Long = 0
    ) {
        val animated = animate && currentState.width != 0
        this.state = state.copy()
        if (applyImmediately || transitionLayout == null) {
            animator.cancel()
            applyStateToLayout(this.state)
            currentState = state.copy(reusedState = currentState)
        } else if (animated) {
            animationStartState = currentState.copy()
            animator.duration = duration
            animator.startDelay = delay
            animator.start()
        } else if (!animator.isRunning) {
            applyStateToLayout(this.state)
            currentState = state.copy(reusedState = currentState)
        }
        // otherwise the desired state was updated and the animation will go to the new target
    }

    /**
     * Set a new state that will be used to measure the view itself and is useful during
     * transitions, where the state set via [setState] may differ from how the view
     * should be measured.
     */
    fun setMeasureState(
        state: TransitionViewState
    ) {
        transitionLayout?.measureState = state
    }
}

class DisappearParameters() {

    /**
     * The pivot point when clipping view when disappearing, which describes how the content will
     * be translated.
     * The default value of (0.0f, 1.0f) means that the view will not be translated in horizontally
     * and the vertical disappearing will be aligned on the bottom of the view,
     */
    var gonePivot = PointF(0.0f, 1.0f)

    /**
     * The fraction of the width and height that will remain when disappearing. The default of
     * (1.0f, 0.0f) means that 100% of the width, but 0% of the height will remain at the end of
     * the transition.
     */
    var disappearSize = PointF(1.0f, 0.0f)

    /**
     * The fraction of the normal translation, by which the content will be moved during the
     * disappearing. The values here can be both negative as well as positive. The default value
     * of (0.0f, 0.2f) means that the content doesn't move horizontally but moves 20% of the
     * translation imposed by the pivot downwards. 1.0f means that the content will be translated
     * in sync with the translation of the bounds
     */
    var contentTranslationFraction = PointF(0.0f, 0.8f)

    /**
     * The point during the progress from [0.0, 1.0f] where the view is fully appeared. 0.0f
     * means that the content will start disappearing immediately, while 0.5f means that it
     * starts disappearing half way through the progress.
     */
    var disappearStart = 0.0f

    /**
     * The point during the progress from [0.0, 1.0f] where the view has fully disappeared. 1.0f
     * means that the view will disappear in sync with the progress, while 0.5f means that it
     * is fully gone half way through the progress.
     */
    var disappearEnd = 1.0f

    /**
     * The point during the mapped progress from [0.0, 1.0f] where the view starts fading out. 1.0f
     * means that the view doesn't fade at all, while 0.5 means that the content fades starts
     * fading at the midpoint between [disappearStart] and [disappearEnd]
     */
    var fadeStartPosition = 0.9f

    override fun equals(other: Any?): Boolean {
        if (!(other is DisappearParameters)) {
            return false
        }
        if (!disappearSize.equals(other.disappearSize)) {
            return false
        }
        if (!gonePivot.equals(other.gonePivot)) {
            return false
        }
        if (!contentTranslationFraction.equals(other.contentTranslationFraction)) {
            return false
        }
        if (disappearStart != other.disappearStart) {
            return false
        }
        if (disappearEnd != other.disappearEnd) {
            return false
        }
        if (fadeStartPosition != other.fadeStartPosition) {
            return false
        }
        return true
    }

    override fun hashCode(): Int {
        var result = disappearSize.hashCode()
        result = 31 * result + gonePivot.hashCode()
        result = 31 * result + contentTranslationFraction.hashCode()
        result = 31 * result + disappearStart.hashCode()
        result = 31 * result + disappearEnd.hashCode()
        result = 31 * result + fadeStartPosition.hashCode()
        return result
    }

    fun deepCopy(): DisappearParameters {
        val result = DisappearParameters()
        result.disappearSize.set(disappearSize)
        result.gonePivot.set(gonePivot)
        result.contentTranslationFraction.set(contentTranslationFraction)
        result.disappearStart = disappearStart
        result.disappearEnd = disappearEnd
        result.fadeStartPosition = fadeStartPosition
        return result
    }
}